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Family name 古家 (古家 , Коя , Кога ) , all over the world, is a very rare cognomen. The family name 古家 is characteristic of Russia, where it is a very rare surname, Kyrgyzstan, and Ukraine. Not in comparison with a country's population, it is the most numerous in Russia, China, and Ukraine. Also, 古家 is the forename as well as the last name.